Method and apparatus for purifying heavy fuel oils



Dec. 19, 1961 H. G. HEMFORT ETAI.

METHOD AND APPARATUS FOR PURIFYING HEAVY FUEL OILS Filed April 12, 1954 2 Sheets-Sheet 1 Fl G- INVENTORS HEINRICH GEORG HEMFORT 8| HEINRICH HUESMANN ATTORNEYS METHOD AND APPARATUS FOR PURIFYING HEAVY FUEL OILS Filed April 12, 1954 Dec. 19, 1961 H. G. HEMFORT ETA].

a Sheets-Sheet 2 INVENTORS' HEINRICH GEORG: HEMFORT a HEINRICH HUESMANN ATTORNEY v 3,013,961 METHGB AND APPARATUS FGR PURIFYING HEAVY FUEL ()IIJS Heinrich Georg Hernfort and Heinrich Huesrnann, Oelde, Westphalia, Germany, assignors to Westfaiia Separator A.G., (icicle, Westphalia, Germany, a corporation of Germany Filed Apr. 12, 1954, Ser. No. 422,641 Claims priority, appiication Germany Apr. 11, 1953 '5 Claims. (Cl. 20S--177) In view of the difference in price between heavy fuel oils and so-called diesel oils, it has been attempted for some time to improve heavy fuel oils in such a manner that they can be used as fuels for diesel engines and gas turbines. These fuel oils or residue oils contain, in addition to the water, the amount of which varies in the case of the individual oils, solid impurities which must be removed for the above-stated purpose.

As non-combustible solids, there are contained in the oils principally earth and metal components which, due to their fineness, cannot be centrifuged out upon the separation of the oils at ordinary temperature. The reason for the retention of these solids in the oil is that, as a result of the high viscosity of fuel oil at normal temperature, a very high frictional force acts against the solid particles which are striving to move outwards. It is known that this frictional force is proportional to the viscosity of the liquid. Inasmuch as, on the other hand, the velocity of separation decreases with increasing frictional force, the solid particles contained in the oil cannot, during their short time of stay in the centrifuge bowl, move over the path necessary for the separation through the oil layer. These solid impurities, due to their abrasive action, cause strong wear of the moving parts of internal combustion engines. In particular, the life of the piston rings and of the cylinders is substantially reduced.

In addition to the non-combustible constituents, there are present in the residue oils as difi'icultly combustible substances mainly sulfur and asphalts. During the combustion process, the sulfur is partially converted into sulfuric acid or sulfurous acid, and in the form of such compounds exerts a destructive action on the machine parts. For this reason alone the practice has been adopted of reducing the injurious effects of the sulfur by surface treatment of the machine parts in question. It is also known to neutralize the acids by the addition of certain agents to the fuel or lubricating oil. The sulfur compounds present in the form of solids can, however, be separated from the oil, together with other impurities by centrifugal separation.

The asphalts are also contained in the form of solids in the fuel oil. The formation of residue caused by them impairs the operation of the internal combustion engines insofar as the slide surfaces of the engines are coated by a tacky layer of this residue and cope particles deposit on the seats of the exhaust valves. It is possible to remove a part of these asphalts from the fuel oil by the centrifuging.

The water content of the oil in particular impairs the ignition quality of the fuel, but a slight water content is of no importance in the case of large diesel engines.

In order to purify fuel oils for the above-stated purpose, it has already been proposed to separate them at temperatures of 80 to 85 C. Such a preheating has the purpose of breaking up any possible emulsions and reducing the, viscosity of the material to be centrifuged. Up to the present time, higher temperatures than these have not been used because at higher temperatures it was feared that there would be a high passing into solution of some of the solids, and particularly the asphalts. On the other hand, it was believed that substances which 3,013,961 Patented Dec. 19, .1961

codetermine the quality of the oil and therefore must remain in the oil, might be separated as solids after chemical decomposition, and centrifuged out of the oil together with the impurities during the separation. The formation of steam, which has a detrimental effect on the separation has undoubtedly also contributed to the fact that up to the present time a centrifuging temperature of more than 100 C. has not been used.

It is known that at temperatures of more than 100 C. volatile components of the oil evaporate. Inasmuch as, however, specifically these components represent the easily ignitable components of the fuel, their loss means a reduction in the quality of the fuel. This fact also appears to have been of great importance in the determination of the centrifuging temperature in the previously known processes.

In accordance with the present invention, a better quality oil is obtained by carrying out the separation at a higher temperature, for example, about 150 C., all valuable substances being retained in the oil. It may be advisable to effect two centrifugings one after the other in this case also, namely at a temperature of less than 100 C. in the first stage in order first of all to remove the Water and coarse impurities from the oil, and at a temperature of more than 100 in the second stage in order to remove the remaining solids from the oil. It has been found that the non-combustible substances can still be considered insoluble, even at temperatures of up to 150 C. On the other hand, the viscosity decreases. substantially with increasing temperature. Thus, for example, a fuel oil of 3500 R1 seconds (Redwood I viscometer) at 100 F. experiences upon heating to 135 C. a reduction of'viscosity down to about 70 RI seconds, which corresponds to a diesel oil of medium viscosity at 38 C. By increasing the operating temperature to 135 C., the viscosity can therefore be reduced to 1/50 of its value at 38 C. As compared with the previous centrifuging temperatures of to C., this temperature increase means a further approximately quadruple increase of the rate of separation. It is therefore possible by increasing the separating temperature to remove by far the largest part of the non-combustible solids from the oil.

Further examinations have shown that the quantity of asphaltic substances which enter into solution at a temperature of C. is not substantially greater than at 85 C. Thus, in the case of the method according to the present invention, a substantially higher removal of the non-combustible solids goes hand in hand with a negligibly smaller inclusion of diflicultly combustible asphalts.

The escape of readily volatile, valuable constituents is either prevented in the manner that the gases and vapors produced in the inlet chamber of the centrifuge are collected, condensed, and again mixed with the purified oil, or else the evaporation itself can be prevented by effecting the introduction of the material to be centrifuged on the inlet side so far below the oil level that the pressure at the place of outlet is greater than the vapor pressure of the readily volatile substances at the operating temperature, while at the outlet side evaporation can be prevented by mixing the purified oil before its outlet from the centrifuge bowl with purified, cooled oil, and cooling to such an extent that no substantial evaporation can take place any more. In case of the treatment of the material to be centrifuged in a purifier bowl in the first separating stage, the evaporation of the water can be prevented by the same means. In this case, water of normal temperature at the water outlet is introduced for cooling purposes into the bowl.

The method and the apparatus of the present invention are shown schematically in the attached drawings, in which:

FIG. 1 is a flow sheet of the process;

FIGS. 2, 3 and 3a show devices for the leading away of the gases and vapors formed in the inlet chamber of the bowl;

FIG. 4 shows a device for preventing the evaporation of water and/or of readily volatile components of the oil on a centrifugal bowl with disc inset.

FIG. 5 shows a device for the same purpose in connection with a chamber bowl.

Figure 1 The fuel oil passes from the crude oil tank 1, in which it is held at a temperature of about 30 C., to heat exchanger 3 via the pump 2. The fuel oil is heated to 90 to 95 C. in the heat exchanger and flows through line a into the centrifugal separator S. The water and the coarse impurities are separated here.

This first centrifugal separator can be equipped with a normal separating bowl or with a bowl which periodically discharges the sludge. The leading away of the separated liquids from the bowl can be effected over over-flow edges or else by peeling discs. The discharging fuel oil is forced by means of a pump 6 or by means of a peeling disc through the heater 7 into the centrifugal separator 8. The fuel oils are heated to, for example, 125 C. in the heater 7. Due to this relatively high temperature, the viscosity of the fuel oil is so reduced that the finer impurities can easily be centrifuged out.

It has been found that at this place there can also advantageously be used a chamber bowl, inasmuch as the water has already been removed and a chamber bowl for the same purifying action has a larger sludge space than a disc bowl. The fuel oil leaves the bowl of the second separator at a temperature of about 120 C. and passes through line 9 to the heat-exchanger 3 where it gives off heat to the incoming fuel oil. Thereupon, the purified fuel oil flows through conduits 10 and 11 to the service tank 12.

In the bowl of separator 8 is provided with a peeling disc for discharging the purified fuel oil, a small part of the purified, cooled fuel oil is advantageously returned through line 13 into the peeling chamber of the separator 8 in order to avoid evaporation losses. In this connection, this liquid stream is so conducted onto the free liquid surface that the cooler fuel oil produces a seal with respect to the atmosphere. A cooler, not shown in the drawing, may be installed in line 13.

Figure 2 The fuel oil flows through the feed line 14 and the inlet pipe 15 into the inlet space 16 of bowl 17. The purified fuel oil leaves the centrifuge space 18 of the bowl through the channel 19, the peeling disc 20, and the discharge line 21. A throttle valve 22 and a pres sure gauge 23 are also provided in the discharge line, so that a continuous dipping of the peeling disc into the liquid can be achieved and controlled. Within the inlet pipe 15 there is arranged another pipe 24, through which the gases and vapors discharge from the inlet space 16 and, after condensation, in a condenser, not shown in the drawing, are again mixed with the purified oil.

Figure 3 FIG. 3 and 3a shows, on the left and 3a on the right, two separate embodiments of the invention.

On the left-hand side, the lower circular limitation 25 of the peeling disc has a smaller diameter than the peeling channels 26 or the upper circulation limitation 27. Due to this, the liquid removed by the peeling disc carries the gases and vapors along with it.

On the right-hand side of FIG. 3, in the lower circular delimitation 25, there is arranged a channel 28, which connects the inlet space of the bowl with the peeling channels in such a manner that the gases and vapors are carried along.

Figure 4 FIG. 4 shows an apparatus for preventing the evaporation of water and/or the easily volatile components of the oil in the inlet space of the bowl and at the bowl outlet. The material to be centrifuged is introduced through the channel 29 and flows at the lower end through the openings 30 into the inlet space 31 of the distributor 32. The openings 30 discharge at a suflicient distance below the oil level, so that the pressure at this place is greater than the vapor pressure of the water and of the easily volatile components at the operating temperature. After separation of the oil-water mixture into its two components, the oil passes through channel 33 into the peeling chamber 34. Purified cool oil is introduced into the peeling chamber through the channel 35 and sprayed onto the surface of the hot oil. The easily volatile components are condensed in the layer of cool oil and can there fore not escape from the oil. The oil is discharged out of the bowl through channel 36. The water which has been removed from the oil flows through channels 37 into space 38. The cooling water introduced through channel 39 passes at 40 into the water trap, together with the water separated from the oil. The same bowl can also be used as clarifier by closing the channels 37 by means of closure plugs 41.

The apparatus can also be used in bowls in connection with which both components discharge freely.

Figure 5 FIG. 5 shows the same device in the case of a chamber bowl as clarifier. The prepurified oil flows through the inlet pipe 42 and the openings 43 into the inlet space 44 of the drum. While the solid impurities deposit on the chamber walls 45, the purified oil is discharged from the peeling chamber 46 through the collector 47 into line 48. Cooled oil is introduced into the peeling chamber 46 through channel 49, the oil being sprayed through openings 50 onto the surface of the hot oil.

The apparatus in accordance with the invention can also be used in connection with a chamber bowl which is arranged as a purifier.

We claim:

1. A method for the use of a centrifugal separator provided with a stripping disc in the purification of heavy fuel oils for use in internal combustion engines and turbines, which comprises centrifugally removing impurities from such oils in said separator at a temperature in excess of C., mixing gases and vapors passed off from said oil with purified oil in said stripping disc, removing purified oil from said separator by means of said stripping disc, passing the removed purified oil in indirect heat exchange contact with fresh oil to be purified in order to impart heat to said fresh oil and to cool said purified oil, and recycling a portion of said cooled, purified oil into said centrifugal separator.

2. A method in accordance with claim 1, which includes preliminarily, centrifugally separating a portion of the impurities from such oils in a preliminary centrifugal separator at a temperature of less than 100 C., and thereafter passing said partially purified oil to said centrifugal separator for the removal of impurities therein at a temperature in excess of 100 C.

3. A method in accordance with claim 2, in which the centrifugal separator which separates at a temperature in excess of 100 C. is provided with a chamber bowl.

4. A method in accordance with claim 1, which includes introducing the oil to be purified into said centrifugal separator at a point sufiiciently far below the surface of the oil therein that the pressure prevailing at the point of removal of said oil is greater than the vapor pressure of the easily volatile components of said oil and of any water present in said oil at the operating temperature of said centrifugal separator.

5. A method in accordance with claim 1, which includes recycling 2. portion of cooled, purified oil onto the surface of the purified oil being removed by means of said Stripping disc.

References Cited in the file of this patent 5 UNITED STATES PATENTS 1,411,782 Hall Apr. 4, 1922 1,474,629 Hall Nov. 20, [1923 1,482,229 Hapgood J an. 29, 1924 10 1,699,379 Sperry Ian. 15, 1929 6 Turner Feb. 20, 1934' Edvarsson Dec. 19, 1944 Jones Sept. 17, 1946 Lindgren Jan. 30, 1951 Andersson Oct. 23, 1951 Eckers June 10, 1952 Staafi Feb. 10, 1953 Peltzer Feb. 9, 1954 FOREIGN PATENTS Great Britain June 27, 1951 

1. A METHOD FOR THE USE OF A CENTRIFUGAL SEPARATOR PROVIDED WITH A STRIPPING DISC IN THE PURIFICATION OF HEAVY FUEL OILS FOR USE IN INTERNAL COMBUSTION ENGINES AND TURBINES, WHICH COMPRISES CENTRIFUGALLY REMOVING IMPURITIES FROM SUCH OILS IN SAID SEPARATOR AT A TEMPERATURE IN EXCESS OF 100*C., MIXING GASES AND VAPORS PASSED OFF FROM SAID OIL WITH PURIFIED OIL IN SAID STRIPPING DISC, REMOVING PURIFIED OIL FROM SAID SEPARATOR BY MEANS OF SAID STRIPPING DISC, PASSING THE REMOVED PURIFIED OIL IN INDIRECT HEAT EXCHANGE CONTACT WITH FRESH OIL TO BE PURIFIED IN ORDER TO IMPART HEAT TO SAID FRESH OIL AND TO COOL SAID PURIFIED OIL, AND RECYCLING A PORTION OF SAID COOLED, PURIFIED OIL INTO SAID CENTRIFUGAL SEPARATOR. 